Field of the Invention
The present invention relates to non-geostationary (non-GEO) satellite (usually medium-earth orbit, MEO, or low-earth orbit, LEO) constellation hand-off (SHD) and diversity-combining (DC) device, the combination being referred to as an SHDC device, used by earth-station satellite receivers.
Background of the Related Art
In U.S. Pat. No. 9,130,644 (the '644 Patent), satellite antennas 14, 24 may include a SHDC device that has both a seamless satellite hand-off device (SHD) 30 (see FIGS. 2, 5) and a diversity combiner (DC) 50 (see FIGS. 3, 5). An Antenna Controller Unit (ACU) controls the sequence of antenna movements including hand-off (e.g., FIGS. 1(a) and 1(b)), tracking the satellite 5 as it continues in its orbit (e.g., FIGS. 1(b) and 1(c)), and the left antenna 14 dropping its signal with the current satellite 5 and beginning to move to find a new ascending satellite (e.g., FIG. 1(d)). This physical layer method of hand-off avoids use of any overheads (pilots, time-stamps, etc.) that are required by other types of hand-off schemes. Hand-offs in LEO satellite constellations occur much more frequently than in MEO satellite constellations. Hence, the duty cycle of the DC goes down, but it is still better than not doing DC at all. U.S. Pat. No. 9,130,644 is hereby incorporated by reference.